Purification and properties of the nicotinamide–adenine dinucleotide phosphate-dependent isocitrate dehydrogenase from pig liver cytoplasm

1970 ◽  
Vol 119 (5) ◽  
pp. 805.b1-805.b1
Keyword(s):  
Isocitrate Dehydrogenase ◽  
Nicotinamide Adenine Dinucleotide ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Nicotinamide Adenine ◽  
Pig Liver ◽  
Purification And Properties

scholarly journals Purification and properties of the nicotinamide–adenine dinucleotide phosphate-dependent isocitrate dehydrogenase from pig liver cytoplasm

1970 ◽  
Vol 118 (2) ◽  
pp. 253-258 ◽  
Author(s):  
J. A. Illingworth ◽  
K. F. Tipton
Keyword(s):  
Molecular Weight ◽  
Amino Acid ◽  
Isocitrate Dehydrogenase ◽  
Nicotinamide Adenine Dinucleotide ◽  
Soluble Fraction ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Turnover Number ◽  
Pig Liver ◽  
Extinction Coefficients ◽  
Purification And Properties

The NADP-dependent isocitrate dehydrogenase from pig liver soluble fraction was purified over 500-fold with an overall yield of 25%. The purified enzyme, which is homogeneous by all the usual criteria, has a molecular weight of about 75000 and is composed of two identical subunits. This has been demonstrated by ultracentrifugation, fluorescence titration and peptide `fingerprinting'. The maximal turnover number, extinction coefficients at 280nm and 260nm and amino acid analysis are described.

scholarly journals The role of nicotinamide–adenine dinucleotide phosphate-dependent malate dehydrogenase and isocitrate dehydrogenase in the supply of reduced nicotinamide–adenine dinucleotide phosphate for steroidogenesis in the superovulated rat ovary

1970 ◽  
Vol 117 (1) ◽  
pp. 73-83 ◽  
Author(s):  
A. P. F. Flint ◽  
R. M. Denton
Keyword(s):  
Malate Dehydrogenase ◽  
Isocitrate Dehydrogenase ◽  
Nicotinamide Adenine Dinucleotide ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Nicotinamide Adenine ◽  
Tissue Homogenate ◽  
Kinetic Properties ◽  
Rat Ovary ◽  
Glucose 6 Phosphate Dehydrogenase ◽  
Effect Of Glucose

1. Superovulated rat ovary was found to contain high activities of NADP–malate dehydrogenase and NADP–isocitrate dehydrogenase. The activity of each enzyme was approximately four times that of glucose 6-phosphate dehydrogenase and equalled or exceeded the activities reported to be present in other mammalian tissues. Fractionation of a whole tissue homogenate of superovulated rat ovary indicated that both enzymes were exclusively cytoplasmic. The tissue was also found to contain pyruvate carboxylase (exclusively mitochondrial), NAD–malate dehydrogenase and aspartate aminotransferase (both mitochondrial and cytoplasmic) and ATP–citrate lyase (exclusively cytoplasmic). 2. The kinetic properties of glucose 6-phosphate dehydrogenase, NADP–malate dehydrogenase and NADP–isocitrate dehydrogenase were determined and compared with the whole-tissue concentrations of their substrates and NADPH; NADPH is a competitive inhibitor of all three enzymes. The concentrations of glucose 6-phosphate, malate and isocitrate in incubated tissue slices were raised at least tenfold by the addition of glucose to the incubation medium, from the values below to values above the respective Km values of the dehydrogenases. Glucose doubled the tissue concentration of NADPH. 3. Steroidogenesis from acetate is stimulated by glucose in slices of superovulated rat ovary incubated in vitro. It was found that this stimulatory effect of glucose can be mimicked by malate, isocitrate, lactate and pyruvate. 4. It is concluded that NADP–malate dehydrogenase or NADP–isocitrate dehydrogenase or both may play an important role in the formation of NADPH in the superovulated rat ovary. It is suggested that the stimulatory effect of glucose on steroidogenesis from acetate results from an increased rate of NADPH formation through one or both dehydrogenases, brought about by the increases in the concentrations of malate, isocitrate or both. Possible pathways involving the two enzymes are discussed.

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